Ste20-like protein kinase SLK (LOSK) regulates microtubule organization by targeting dynactin to the centrosome

Mol Biol Cell. 2013 Oct;24(20):3205-14. doi: 10.1091/mbc.E13-03-0137. Epub 2013 Aug 28.

Abstract

The microtubule- and centrosome-associated Ste20-like kinase (SLK; long Ste20-like kinase [LOSK]) regulates cytoskeleton organization and cell polarization and spreading. Its inhibition causes microtubule disorganization and release of centrosomal dynactin. The major function of dynactin is minus end-directed transport along microtubules in a complex with dynein motor. In addition, dynactin is required for maintenance of the microtubule radial array in interphase cells, and depletion of its centrosomal pool entails microtubule disorganization. Here we demonstrate that SLK (LOSK) phosphorylates the p150(Glued) subunit of dynactin and thus targets it to the centrosome, where it maintains microtubule radial organization. We show that phosphorylation is required only for centrosomal localization of p150(Glued) and does not affect its microtubule-organizing properties: artificial targeting of nonphosphorylatable p150(Glued) to the centrosome restores microtubule radial array in cells with inhibited SLK (LOSK). The phosphorylation site is located in a microtubule-binding region that is variable for two isoforms (1A and 1B) of p150(Glued) expressed in cultured fibroblast-like cells (isoform 1B lacks 20 amino acids in the basic microtubule-binding domain). The fact that SLK (LOSK) phosphorylates only a minor isoform 1A of p150(Glued) suggests that transport and microtubule-organizing functions of dynactin are distinctly divided between the two isoforms. We also show that dynactin phosphorylation is involved in Golgi reorientation in polarized cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Polarity / genetics
  • Centrosome / metabolism*
  • Centrosome / ultrastructure
  • Chlorocebus aethiops
  • Cytoskeleton / genetics*
  • Cytoskeleton / metabolism
  • Cytoskeleton / ultrastructure
  • Dynactin Complex
  • Dyneins / metabolism
  • Fibroblasts / cytology
  • Fibroblasts / metabolism
  • Golgi Apparatus / ultrastructure
  • HeLa Cells
  • Humans
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / genetics*
  • Microtubules / metabolism
  • Microtubules / ultrastructure
  • Phosphorylation
  • Protein Isoforms / genetics
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism
  • Vero Cells

Substances

  • DCTN1 protein, human
  • Dynactin Complex
  • Microtubule-Associated Proteins
  • Protein Isoforms
  • Protein Kinases
  • SLK protein, human
  • p150 protein kinase
  • Protein-Serine-Threonine Kinases
  • Dyneins